Evaluation of sensibility and specificity of NIR transillumination for early enamel caries detection - An in vitro study

Proximal surface lesions are not very often detected by X-ray examination, suggesting the predominance of a subjective diagnosis on the part of the dentist. Since the magnitude of light scattering within the tooth decreases exponentially at longer wavelengths, evaluation of transillumination by near infra red lasers is a new alternative noninvasive technique to detect and quantify demineralization of lesions. After the Ethics Committee approved the study, fourteen crowns of extracted teeth with white spot lesions as sign of demineralization were collected at the Human Teeth Bank of the Departament of Prothesis and Dental-Facial Surgery of the Universidade Federal de Pernambuco. Sections of various thickness, between 1.5 to 5 mm, were cut in a bucal-lingual plane, preserving white spots lesions. Our home-built NIR transillumination system set up consisted of a broadband light source at two different wavelengths (1280 nm and 1400 nm), crossed linear polarizers, lenses and the Micron Viewer IR camera (CCD). All samples were imaged by NIR transillumination system and the conventional technique, X-ray, and all images were analyzed by two experienced examiners. Results were checked with stereomicroscope images as a "gold standard", making the determination of sensitivity (proportion of cases correctly identified as positive) and specificity (proportion of disease-free cases correctly identified as negative) possible. The interexaminer reproducibility (Kappa test statistic) showed moderate association for NIR TI technique, and low association for X-ray. The results from the NIR TI were better than those from X-ray, with respect to both sensitivity and specificity, even though the examiners had less experience with the NIR system. This research promotes findings into clinically relevant measures of early caries disease diagnosis and can be used to monitor caries progression during patient follow up. Furthermore, without the use of ionizing radiation, NIR TI can be repeated without risk, offering a better means for caries diagnosis in the future.